“ Capitalist production does not exist at all without foreign commerce. ”
 Karl Marx, Das Kapital (1885). copy citation

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“The capitalist countries of Europe obtain almost all their gold, and by far the greater part of their silver, from Australia, the United States, Mexico, South America, and Russia. But we take it that the gold mines are in a country with capitalist production whose annual reproduction we are here analysing, and for the following reasons: Capitalist production does not exist at all without foreign commerce. But when one assumes normal annual reproduction on a given scale one also assumes that foreign commerce only replaces home products by articles of other use or bodily form, without affecting value-relations, hence without affecting either the value-relations in which the two categories” source